/****************************************************************************
 * libs/libc/stdlib/lib_strtod.c
 * Convert string to double
 *
 *   Copyright (C) 2002 Michael Ringgaard. All rights reserved.
 *   Copyright (C) 2006-2007 H. Peter Anvin.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the project nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

//#include <nuttx/config.h>
//#include <nuttx/compiler.h>

#include <stdlib.h>
#include <ctype.h>
#include <errno.h>

#define CONFIG_HAVE_DOUBLE
#define FAR

#ifdef CONFIG_HAVE_DOUBLE

/****************************************************************************
 * Pre-processor definitions
 ****************************************************************************/

/* These are predefined with GCC, but could be issues for other compilers. If
 * not defined, an arbitrary big number is put in for now.  These should be
 * added to nuttx/compiler for your compiler.
 */

#if !defined(__DBL_MIN_EXP__) || !defined(__DBL_MAX_EXP__)
#  ifdef CONFIG_CPP_HAVE_WARNING
#    warning "Size of exponent is unknown"
#  endif
#  undef  __DBL_MIN_EXP__
#  define __DBL_MIN_EXP__ (-1021)
#  undef  __DBL_MAX_EXP__
#  define __DBL_MAX_EXP__ (1024)
#endif

/****************************************************************************
 * Private Functions
 ****************************************************************************/

static inline int is_real(double x)
{
	const double infinite = 1.0/0.0;
	return (x < infinite) && (x >= -infinite);
}

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/***************************************************(************************
 * Name: strtod
 *
 * Description:
 *   Convert a string to a double value
 *
 ****************************************************************************/

double lib_strtod(FAR const char *str, FAR char **endptr)
{
	double number;
	int exponent;
	int negative;
	FAR char *p = (FAR char *) str;
	double p10;
	int n;
	int num_digits;
	int num_decimals;
	const double infinite = 1.0/0.0;

	/* Skip leading whitespace */

	while (isspace((unsigned char)(*p)))
	{
		p++;
	}

	/* Handle optional sign */

	negative = 0;
	switch (*p)
	{
	case '-':
		negative = 1; /* Fall through to increment position */
		/* FALLTHROUGH */
	case '+':
		p++;
		/* FALLTHROUGH */
	default:
		break;
	}

	number       = 0.;
	exponent     = 0;
	num_digits   = 0;
	num_decimals = 0;

	/* Process string of digits */

	while (isdigit((unsigned char)*p))
	{
		number = number * 10. + (*p - '0');
		p++;
		num_digits++;
	}

	/* Process decimal part */

	if (*p == '.')
	{
		p++;

		while (isdigit((unsigned char)*p))
		{
			number = number * 10. + (*p - '0');
			p++;
			num_digits++;
			num_decimals++;
		}

		exponent -= num_decimals;
	}

	if (num_digits == 0)
	{
		//set_errno(ERANGE);
		number = 0.0;
		goto errout;
	}

	/* Correct for sign */

	if (negative)
	{
		number = -number;
	}

	/* Process an exponent string */

	if (*p == 'e' || *p == 'E')
	{
		/* Handle optional sign */

		negative = 0;
		switch (*++p)
		{
			case '-':
				negative = 1;   /* Fall through to increment pos */
				/* FALLTHROUGH */
			case '+':
				p++;
				/* FALLTHROUGH */
			default:
				break;
		}

		/* Process string of digits */

		n = 0;
		while (isdigit((unsigned char)*p))
		{
			n = n * 10 + (*p - '0');
			p++;
		}

		if (negative)
		{
			exponent -= n;
		}
		else
		{
			exponent += n;
		}
	}

	if (exponent < __DBL_MIN_EXP__ ||
			exponent > __DBL_MAX_EXP__)
	{
		//set_errno(ERANGE);
		number = infinite;
		goto errout;
	}

	/* Scale the result */

	p10 = 10.;
	n = exponent;
	if (n < 0)
	{
		n = -n;
	}

	while (n)
	{
		if (n & 1)
		{
			if (exponent < 0)
			{
				number /= p10;
			}
			else
			{
				number *= p10;
			}
		}

		n >>= 1;
		p10 *= p10;
	}

	if (!is_real(number))
	{
		//set_errno(ERANGE);
	}

errout:
	if (endptr)
	{
		*endptr = p;
	}

	return number;
}

double __wrap_strtod(FAR const char *str, FAR char **endptr)
{
	return lib_strtod(str, endptr);
}

#endif /* CONFIG_HAVE_DOUBLE */
